One of the features of the present invention is the ability, in context of a dual-deck VCR system, to duplicate "high quality" videocassette tapes (specifically, those videocassette tapes with azimuth recording characteristics as used in home-consumer VCR's) with good fidelity and avoidance of copy degradation where a copy is made from a copy in two or more generations.
A further feature of the invention is the maintenance of the integrity of pre-encoded copyright protection systems in a manner that makes defeat of protection systems by ordinary consumer devices (generally referred to as "video stabilizers" or "black boxes") impracticable.
The user of the consumer grade azimuth-recorded videocassette tapes can, with this invention, simply and easily duplicate (or dub) tape contents from one (source tape) to the other (target tape) through FM dub circuitry provided in this invention to achieve a clear, high-quality, videocassette target tape which is indistinguishable from the original (source) videocassette tape. Further, several generations of duplicated videocassette tapes maintain the high quality visual characteristics of the original videocassette recording.
Azimuth-recorded videocassette tapes can, with the present invention, be pre-encoded with a signal (or various signals) that actuate the circuitry of the dual-deck VCR system to prevent the duplication of said tapes (through a closed, sealed circuit device which makes it impracticable and cost prohibitive for the consumer to bypass this system and impossible to use a video stabilizer and still maintain the quality as provided by the dub circuitry of the invention).
Commercial "reel-to-reel" videotape recording (VTR) was introduced to the public by the U.S. company, Ampex, Inc., in 1956. In 1969 Sony Corporation (Japan), and its U.S. marketing subsidiary, introduced the first 3/4-inch U-Matic "videocassette" recording (VCR) unit for commercial broadcast TV studio recording purposes. These systems although excellent for broadcast TV studio purposes had major drawbacks for home-consumer uses (i.e., expensive, occupied too much space-large footprint, cumbersome, complicated to use, short recording time capacity). This capacity problem and some portion of the other shortcomings were caused by the excessive space required in the recording method used to lay the signal on the videotape. Space needs were generated by (1) the large size of the recording heads' gap (85 microns) and (2) the necessity of a guard band (the unrecorded space or distance between the recorded information of the video track) on the tape to prevent "cross-talk."
Although azimuth recording was patented in 1958 it wasn't perfected until 1974 when Sony introduced the Betamax brand 1/2-inch VCR designed for the home consumer and comprising the feature that slant azimuth recording was incorporated into videocassette recorders by using smaller narrow gapped heads (58 microns). Azimuth recording uses two heads mounted with head gaps at angles slightly off perpendicular to the head path (at a six degree angle to true perpendicular to direction of the head), one slanted to the left and the other to the right. This azimuth head configuration reduces cross-talk and eliminates the wasted, unused space that was required on the bulky commercial VTR's and 3/4-inch VCR's.
Matsushita and Victor Company of Japan (JVC) immediately introduced their version of a consumer VCR format, viz: 1/2-inch VHS (Video Home Systems), which incorporated the azimuth recording system but also extended the recording time to six hours using T-120 tape or eight hours using T-160 tape. This was accomplished by using a smaller recording head gap (29 microns), by creating a one-half track width and by slowing down the running speed of the tape.
VCR technology was then commercially practicable at a consumer market level as the cost had been reduced, the machines were smaller, the cassettes were pocket book size, the loading of tapes and operations was now simple and a long series of television programs could be recorded. With the addition of a tuner/timer, time shifting was available so the user could watch programs during leisure time.
The introduction of VHS and Beta for consumer recording of broadcast television shows immediately raised the question of legality of selling the VCR machines, which was resolved by a U.S. Supreme Court decision in 1984 (Sony Corp. of America v. Universal Studios, 464 U.S. 417 (1984), favor of continued sale. The door was opened for order of magnitude expansion in the U.S. sale of VCR's. This was followed by a proliferation of videocassette recordings from various sources (i.e., home movies, business productions, educational programs, news releases, etc.) and many VCR owners began wiring their single deck machines together to make copies of their tapes. However, the quality of the copies made by wiring two VCR's was and is marginal.
A major problem of such copying was and is the inability to effectively transfer an azimuth recorded video signal and lay it on a blank tape in the same azimuth format without loss of signal, the creation of noise and the experience of severe degradation of signal. Several efforts of the art to solve the problem included video enhancers, detailers and other such means to fill in or alter signals but none of these devices could "save" the original azimuth recorded signal in an unaltered state for duplication of like kind and quality.
It is, therefore, the object of the present invention to overcome the prior-art drawbacks of dubbing technique and apparatus.
It is a further object of the invention to enhance the usefulness of videocassette recorder (VCR) systems.
It is a further object of the invention to provide a low cost, mass-marketable dual deck videocassette recorder system which is easy to understand and use, reliable and multi-functional, with a range of selectable useful operations for entertainment, educational and/or business purposes.